# New Additions to the Interactive Math Page

I’ve added two new links to the Interactive Math page:

- Secant lines to tangent lines. Learn how secant lines (lines through two points on a graph) are used to introduce the derivative in calculus. You’ll get to interact with a graph and see how a tangent line (whose slope is the derivative) emerges by making the two points a secant line passes through closer together.

- The calculus of cooling coffee. Read about the calculus that helps explain why coffee cools down so quickly.

Both additions are related to content from my book, *Everyday Calculus.* Visit the Interactive Math page to find out more.